Heat pipe technology is old art incorporating the use of an evacuated sealed metal pipe partially filled with a working fluid. A wide variety of working fluids may be used; they are selected to be compatible with the temperature regime of the two heat transfer pairs between which heat is being transferred. The heat source must be able to evaporate the working fluid while the heat sink must be able to condense the vapor back into a liquid. Heat pipes also typically contain an internal wick coating to return condensed working fluid back to the heated evaporator zone. While heat pipes are relatively inexpensive to manufacture and offer orders of magnitude effective thermal conductivity as compared to solid copper of similar size, there are some limitations to their physical construction for proper operation.
Heat pipes typically degrade in performance as the tube length increases. Increasing tube diameter can help alleviate this issue, but larger tubes come with their own inefficiencies. It is known that smaller tubes offer greater efficiency, but in heat pipes smaller tubes restrict the length of the tube. Longer heat pipes of smaller diameter, if practical, would offer an opportunity to construct cost-competitive compact and efficient air-to-air heat exchangers.
U.S. Pat. No. 5,913,360 of Stark describes a heat exchanger with cooling coil fins 47 in FIGS. 6 and 7. The cooling coil fins are not baffles separating air streams. In addition, Stark '360 shows in FIG. 6 a cooling coil 66 which is an evaporator only. There are no condenser zones in cooling coil 66 of Stark '360. Stark '360 does not in FIG. 6 any uninterrupted extended length or serpentine heat exchanger 66, and does not describe multiple adjacent evaporator/condenser zones
In U.S. Pat. No. 5,921,315, inventor Khanh Dinh describes a heat exchanger of serpentine pipes where there is no external airside air flow affecting the heat exchange inside of Dinh's apparatus.
Dinh '315 also makes an observation which he illustrates in a figure similar to prior art FIG. 12 of this invention. Heat pipe heat exchanger 58 uses serpentine heat pipe 56 formed by U-bends 51 connecting adjacent straight sections 50 of pipe or tube which are embedded in heat conducting fins 52. Each tube 50 is shown with optional internal microgrooves 53 to enhance heat transfer.
Dinh '315 notes that it had been thought that inserting a predetermined amount of refrigerant 54 into the open end of edge tube 55 of serpentine 56 to permit each tube 50 to function as a separate heat pipe in steady state would require the use of a manifold to properly distribute the refrigerant. However, Dinh '315 discovered that no manifold was necessary and that by inserting the proper amount of refrigerant 54 in edge tube 55 it would become evenly distributed in tubes 50 (as shown) after a few minutes of normal operation of heat exchanger 58. Thus a single charging port can be used with a serpentine heat pipe heat exchanger without the use of any straight pipe manifolds.
U.S. Pat. No. 4,299,272 of Del Bagno, describes an Industrial Heat Pipe Recovery Package Unit “which is easily cleaned to remove contaminants which have collected on the finned heat exchange units” (col. 1, penultimate paragraph) so that brackets 302 and 305 “facilitate heat tube placement, insertion and removal” (col. 3, last par.). Del Bagno '272 does not teach or suggest a baffle arrangement being used to separate the heat transfer fluids flowing over the outside of the heat pipe. In Del Bagno there is shown an industrial heat pipe energy recovery package unit “which is easily cleaned to remove contaminants which have collected on the finned heat exchange units” (col. 1, penultimate paragraph) so that brackets 302 and 305 “facilitate heat tube placement, insertion and removal” (col. 3, last par.). Del Bagno's brackets do not separate multiple, adjacent air flows into multiple adjacent evaporator/condenser zones influenced by exterior air side air streams
Del Bagno '272 shows in FIG. 1 a single pair of two opposing air streams 100 and 200, traveling through a heat pipe heat exchanger 230. Both opposing air streams 100 and 200 have the ability to bypass the heat exchanger through the use of face and bypass assemblies 130 and 210 in the intake and exhaust airstreams. Del Bagno '272 identifies the air streams 100 and 200 as “SUPPLY SIDE” 100 and “EXHAUST SIDE” 200. Del Bagno '272 identifies these two air streams as a single supply side 100 and a single exhaust side 200
Del Bagno '272 also comprises a spray chamber 220, shown in FIGS. 2 and 3. The spray chamber 220 is shown in the exhaust air stream in FIG. 2, which comprises essentially one half of the spray chamber, while the remaining half allows the intake air to pass unimpeded. FIG. 4 of Del Bagno '272 also shows structural tube supports 302, 305 that are required to keep the heat tubes straight and free from sagging when the tube length exceeds a specified length. A single center divider made of structural tube supports 302, 305 is shown in FIG. 4 of Del Bagno '272 to divide the single intake air stream and the single exhaust air stream, while also serving to support the tubes 301. The same mechanism is used for the sole purpose of supporting the tubes to the left and right of center.
In connection therewith, Del Bagno '272 states at column 3, lines 49, 50 as “mounting brackets 302 and 305”. Del Bagno continues to state from column 3, line 68 to column 4, line 10 as follows:
“The bracket assembly comprises two end brackets 302 and one more intermediate brackets 305 whose number will vat), according to the row depth requirements of the specific application. The brackets are provided with mounting flanges 303 on their ends and spaced tube receiving recesses 304 along their sides. In their assembled relationship the recesses 304 in the respective brackets form circular apertures 306 which secure the heat tubes in place and accommodate the integral finned surface 301 on the heat tube.”
Clearly Del Bagno teaches a single air supply input stream 100 and a single air exhaust stream 200, as shown in FIGS. 1, 2 and 4 therein. They are clearly marked in Del Bagno '272 as two counterflow air streams, one hot and one cold.